Field of the Invention
The present invention relates to a manufacturing method and a manufacturing apparatus of a support for a planographic printing plate, particularly relates to an alkaline etching treatment using an alkaline solution applied to a low purity aluminum web, and relates to an acid etching treatment using an acid electrolytic solution applied to an aluminum web.
Description of the Related Art
In general, an aluminum support for a planographic printing plate (referred to as a “support for a planographic printing plate”, hereinafter) is manufactured by graining (surface roughening treatment) at least one surface of an aluminum web that is a thin web plate, and forming an anodic oxidation film on this roughened surface formed through the surface roughening treatment. A thin plate of pure aluminium or an aluminum alloy with purity of 99.5 wt % or more is commonly used as a material of an aluminum web to be manufactured into support for a planographic printing plate.
For the purpose of applying a function of a planographic printing plate for an application to the spread of the CTP (computer to plate) technology, impurities (dissimilar metal) may be added in aluminum. In the viewpoint of energy saving, it has been studied on that a support for a planographic printing plate is manufactured by utilizing recycled aluminum ground metal made from scrap materials or recycled materials of planographic printing plates.
The roughened surface of the support of a planographic printing plate produced as described above is coated with a plate-making layer forming solution such as a photosensitive layer forming solution and a heat-sensitive layer forming solution, and is dried so as to produce a photosensitive or heat-sensitive printing surface. In this manner, a web for a planographic printing plate is manufactured.
In the above mentioned roughened surface, a surface of an aluminum web is normally provided with a brush graining treatment for roughening the surface; an alkaline etching treatment for processing the aluminum web with an alkaline solution so as to dissolve a surface layer thereof; and an electrolytic surface roughening treatment for applying AC electrolysis to an aluminum web in an acid electrolytic solution.
In the an anode oxidation film treatment, DC electrolysis is applied to an aluminum web in anode oxidation treatment solution containing a strong acid such as a sulphuric acid solution, a phosphoric acid solution, and a sulfonic acid solution as an acid component.
Japanese Patent Application Laid-Open No. 2004-066650 discloses an alkaline etching technique. In a manufacturing method of a support for a planographic printing plate, Japanese Patent Application Laid-Open No. 2003-112484 discloses a brush graining treatment for roughening a surface of an aluminum web, an electrolytic surface roughening treatment for carrying out AC electrolysis on an aluminum web in an acid electrolytic solution, an anode oxidation treatment for forming an anode oxidation film on an aluminum web in an acid solution.
Unfortunately, in an alkaline etching treatment, although composition concentration of an alkaline solution cyclically used is adjusted at a constant level, the etching performance gradually becomes deteriorated while the alkaline solution is being cyclically used.
Deterioration of the etching performance varies hole diameter distributions of pits formed on a roughened surface of an aluminum web, which hinders a constant quality level of a support for a planographic printing plate. Consequently, this deteriorates the printing resistance and the fouling resistance of a planographic printing plate manufactured as a finished product.
In acid etching, since an aluminum material constituting an aluminum web contains not a few impurities, various kinds of solid matters resulted from such impurities (intermetallic compounds or deposits) may be generated in an acid electrolytic solution used in an electrolytic surface roughening treatment, or an acid solution used in an anode oxidation treatment. Such generated solid matters are precipitated onto rollers, and may be transferred or cause flaws on the aluminum web, or generate an uneven roughened surface of the aluminum web, which may result in defects on an anode oxidation film thereof.
These disadvantages in the alkaline etching and the acid etching become notable particularly in use of a low purity aluminum web such as an aluminum web having low purity of 99.4 wt % or less, particularly 99.0 wt % or less (98.5 wt %, for example).
In some cases, impurities (dissimilar metal) are added in aluminum for the purpose of applying a function of a planographic printing plate for an application to the CTP (computer to plate). In the viewpoint of energy saving, it has been studied on that a support for a planographic printing plate is manufactured by utilizing recycled aluminum ground metal made of scrap materials or recycled materials of planographic printing plates.